Ehm... well... I did not state you had to remove the other repositories, just add the missing one. Indeed the oss and the non-oss repositories are necessary. For your convenience, here is a list of the repositories enabled on my system:
Name URL Priority
openSUSE-11.1-Oss http://download.opensuse.org/distribution/11.1/repo/oss/ 100
openSUSE-11.1-Non-Oss http://download.opensuse.org/distribution/11.1/repo/non-oss/ 100
openSUSE-11.1-Update http://download.opensuse.org/update/11.1/ 20
Packman Repository http://ftp.skynet.be/pub/packman/suse/11.1/ 99
NVIDIA Repository http://download.nvidia.com/opensuse/11.1 99
Libdvdcss repository http://suse.linuxin.dk/repo/11.1/ 99
Please note, the first three are essential in order to install opensuse packages and keep them up-to-date. Also note that they don't necessarily point to the official opensuse server, but they are automatically redirected to a mirror in your vicinity.
Regarding the Packman repository, it is a well known opensuse additional repository with a lot of additional software, especially to give full multimedia capabilities. You can safely add this repository, and choose a mirror different than mine, depending on where you are located.
The libdvdcss is a repository which provides the libdvdcss library to enable the access to DVD (you can play commercial DVDs on your computer, through mplayer or vlc for example) despite their encryption.
Finally, I enabled the NVIDIA repository since I chosed to install the proprietary drivers for my NVIDIA card and I want to keep them up-to-date.
In summary - the first three repositories are necessary. The Packman repository is strongly suggested. The others depend on your choice and your needs.